4.51 release notes

This is a minor bugfix release, in preparation for the next major
merge. Fixes:
* Use argument 'draft' for document instead of 'approved_draft_name' when
sending sync notifications to the RFC-Editor.
* Moved settings for RFC-Editor sync to settings.py.
* Don't actually do a post to the rfc-editor's state sync interface for a
publication request when not in production mode.
* Merged [5770] from rjsparks@nostrum.com:
- Added editing last call messages, requesting, issuing and tracking IETF
LCs to status-change documents
- Added a Cancel button to the form that allows editing the relations for
status-change documents
- Added instructions to the agenda section 3.3
This adds states to status-change- documents and has a migration that
must be applied. Fixes bug #1039
-- Henrik Levkowetz <henrik@levkowetz.com> 09 Jun 2013 22:03:29 +0200